Air Fuel Ratio jumps to 29.40 - 8th Generation Honda Civic Forum
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Old 03-18-2014, 02:28 PM   #1 (permalink)
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Air Fuel Ratio jumps to 29.40

I noticed my A/F ratio jumps to 29.40 from time to time from my datalog...
Is this normal or should I be worried?
I tried searching the forums but didn't find a thread on this.

I'm vit tuned with flashpro
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Old 03-18-2014, 03:30 PM   #2 (permalink)
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Yeah, it's during shifts it will do that. Also, when your exhaust is popping it back flow the air and cause a reading like this also. You are all good.
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Old 03-18-2014, 06:21 PM   #3 (permalink)
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Originally Posted by criminalsi View Post
Yeah, it's during shifts it will do that. Also, when your exhaust is popping it back flow the air and cause a reading like this also. You are all good.
Oh, I see. Thanks man! I've noticed if I'm in neutral, and tap the gas pedal to rev, when the revs come back down to ~1k, it will jump up to ~1.2k and then settle down to ~800. During this time I also get air/fuel ratios of 29.40...
Is this normal as well?
I'm super paranoid
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Old 03-18-2014, 07:15 PM   #4 (permalink)
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When you are in overrun conditions (above certain RPM, foot off gas) the car cuts fuel; no fuel = AFR of infinity, our O2 sensor just maxes out at 29. To prevent the car from stalling, once the RPMS drop past a certain point the injectors are turned back on (in your particular case this would be ~1k) and then the car settles at the idle speed for those conditions.
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Old 03-18-2014, 10:46 PM   #5 (permalink)
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Originally Posted by pepperdanky View Post
When you are in overrun conditions (above certain RPM, foot off gas) the car cuts fuel; no fuel = AFR of infinity, our O2 sensor just maxes out at 29. To prevent the car from stalling, once the RPMS drop past a certain point the injectors are turned back on (in your particular case this would be ~1k) and then the car settles at the idle speed for those conditions.
i understand now. thank you!
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Old 03-19-2014, 09:30 AM   #6 (permalink)
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All good bud.
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